Liquid crystal display panel, method for manufacturing the same and liquid crystal composition

ABSTRACT

An LCD panel, comprises substrates facing each other, a liquid crystal layer disposed between the substrates and liquid crystal alignment layers, each sandwiched between the liquid crystal layer and a respective one of the substrates, wherein the liquid crystal alignment layers comprises hydrocarbon derivative having perfluorocarbon group.

This application claims the priority of and all the benefits accruingunder 35 U.S.C. § 119 from Korean Patent Application No. 10-2015-0007819filed on Jan. 16, 2015 in the Korean Intellectual Property Office(KIPO), the disclosure of which is incorporated herein by reference inits entirety.

BACKGROUND OF THE INVENTION

Field of the Invention

The present disclosure relates to a LCD panel, a method formanufacturing the same and a liquid crystal composition. Morespecifically, the present disclosure relates to a LCD panel includinghydrocarbon derivative having perfluorocarbon group, a method formanufacturing a LCD panel in which a liquid-crystal alignment film isformed by injecting a liquid crystal composition and then performinglight irradiation without performing traditional coating, drying andfiring processes, and a liquid crystal composition containing liquidcrystal molecules and liquid crystal alignment inducing agent.

Description of the Related Art

An LCD (liquid crystal display) device comprises an LCD panel composedof display substrates facing each other and a liquid crystal layersandwiched therebetween.

An LCD panel itself does not emit light and thus requires a light sourcefor illuminating the panel at the back of the panel. The transmittanceof the light supplied to the LCD panel from the light source is adjusteddepending on the orientation of liquid crystal molecules in its liquidcrystal layer.

A known technique for aligning the liquid crystal molecules verticallywith respect to the surfaces of the display substrates employs liquidcrystal alignment films, which are produced by way of coating thesurfaces of the display substrates with a polymer organic compound or aninorganic compound such as silicon oxide to form a thin film, and thenperforming processes such as drying and firing it. Typically, apolyimide-based, vertical alignment thin-film is used as the liquidcrystal alignment film.

To produce such a polyimide-based thin-film, a series of processes hasto be carried out, involving a process of coating the display substrateswith a liquid agent for liquid crystal alignment, which is composed of apolyimide-based compound, a process of drying and a process ofhigh-temperature firing. Such a series of processes, however, results inlow productivity. Therefore, required are simpler processes of producinga liquid crystal alignment film for better productivity.

SUMMARY OF THE INVENTION

Aspects of the present invention provide a method for manufacturing aLCD panel with improved productivity.

Aspects of the present invention also provide a LCD panel capable ofimproving uniformity, stability and reliability of liquid crystalmolecules orientation.

Aspects of the present invention also provide a liquid crystalcomposition containing a liquid crystal alignment inducing agent as anadditive agent.

These and other aspects, embodiments and advantages of the presentinvention will become immediately apparent to those of ordinary skill inthe art upon review of the Detailed Description and Claims to follow.

According to one aspect of the present invention, there is provided anLCD panel, comprising, substrates facing each other, a liquid crystallayer disposed between the substrates and liquid crystal alignmentlayers, each sandwiched between the liquid crystal layer and arespective one of the substrates, wherein the liquid crystal alignmentlayers comprises hydrocarbon derivative having perfluorocarbon group.

According to another aspect of the present invention, there is provideda method for manufacturing an LCD panel, the method comprising,disposing a first substrate and a second substrate such that they faceeach other, injecting a liquid crystal composition containing liquidcrystals and hydrocarbon derivative having perfluorocarbon group betweenthe first substrate and the second substrate and irradiating the liquidcrystal composition with UV ray.

According to yet another aspect of the present invention, there isprovided a liquid crystal composition comprising, liquid crystals andhydrocarbon derivative having perfluorocarbon group.

According to the present disclosure, a liquid crystal alignment film forinducing alignment of liquid crystal molecules can be produced simply byinjecting hydrocarbon derivative having perfluorocarbon group togetherwith liquid crystal molecules between upper and lower substrates or bydropping it onto the upper and lower substrates and then to performlight irradiation. Therefore, a series of traditional processes ofcoating the upper and lower substrates with polymer liquid crystalalignment agent and of drying and firing can be eliminated, improvingproductivity and process efficiency.

Further, since high-temperature processes required in the existingprocess of firing a polymer alignment film is not necessary, LCD devicesemploying flexible organic polymer substrates vulnerable tohigh-temperature process can be easily fabricated.

It should be noted that effects of the present invention are not limitedto those described above and other effects of the present invention willbe apparent to those skilled in the art from the following descriptions.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete appreciation of the invention, and many of the attendantadvantages thereof, will be readily apparent as the same becomes betterunderstood by reference to the following detailed description whenconsidered in conjunction with the accompanying drawings, in which likereference symbols indicate the same or similar components.

This patent or application file contains at least one drawing executedin color. Copies of this patent or patent application publication withcolor drawing(s) will be provided by the USPTO upon request and paymentof the necessary fee.

FIG. 1 is a view showing a layout of an LCD panel according to anexemplary embodiment of the present disclosure;

FIGS. 2 to 8 are cross-sectional views for schematically illustrating aseries of processes of a method for manufacturing the LCD panel shown inFIG. 1, according to an exemplary embodiment of the present disclosure;

FIGS. 9 to 12 are cross-sectional views for schematically illustrating aseries of processes of a method for manufacturing the LCD panel shown inFIG. 1, according to another exemplary embodiment of the presentdisclosure;

FIGS. 13 to 15 are photographs of an LCD panel manufactured according toa first embodiment observed with a polarizing microscope through crossedpolarizers, and FIG. 15 is a conoscopy image of the LCD panel;

FIGS. 16 to 18 are photographs of an LCD panel manufactured according toa first embodiment after the first irradiation, observed with apolarizing microscope through crossed polarizers, showing switching uponapplication of electric field;

FIGS. 19 and 20 are photographs of an LCD panel manufactured accordingto a first embodiment after the second irradiation, observed with apolarizing microscope through crossed polarizers, showing switching uponapplication of electric field;

FIGS. 21 and 22 are photographs of an LCD panel manufactured accordingto a second embodiment after the light stabilization by UV irradiation,observed with a polarizing microscope through crossed polarizers,showing changes in transmittance before and after application ofvoltage, respectively;

FIGS. 23 and 24 are photographs of an LCD panel manufactured accordingto a fourth embodiment after the light stabilization by UV irradiation,observed with a polarizing microscope through crossed polarizers,showing changes in transmittance before and after application ofvoltage, respectively;

FIG. 25 is a photograph of an LCD panel manufactured according to thefifth embodiment, observed with a polarizing microscope;

FIGS. 26 and 27 are photographs according to the fifth embodiment,observed with a polarizing microscope, showing changes in transmittanceupon application of voltage; and

FIGS. 28 to 32 are photographs observed with a polarizing microscope,conoscopy images and photographs showing switching characteristics uponapplication of voltage of a manufactured liquid crystal device in eachof the steps according to a sixth embodiment.

DETAILED DESCRIPTION OF THE INVENTION

Features of the inventive concept and methods of accomplishing the samemay be understood more readily by reference to the following detaileddescription of preferred embodiments and the accompanying drawings. Theinventive concept may, however, be embodied in many different forms andshould not be construed as being limited to the embodiments set forthherein. Rather, these embodiments are provided so that this disclosurewill be thorough and complete and will fully convey the concept of theinventive concept to those skilled in the art, and the inventive conceptwill only be defined by the appended claims.

In the drawings, the thickness of layers and regions are exaggerated forclarity. It will be understood that when an element or layer is referredto as being “on,” “connected to” or “coupled to” another element orlayer, the element or layer can be directly on, connected or coupled toanother element or layer, or one or more intervening elements or layersmay be present. In contrast, when an element is referred to as being“directly on,” “directly connected to” or “directly coupled to” anotherelement or layer, there are no intervening elements or layers present.As used herein, connected may refer to elements being physically,electrically, operably, and/or fluidly connected to each other.

Like numbers refer to like elements throughout. As used herein, the term“and/or” includes any and all combinations of one or more of theassociated listed items.

It will be understood that, although the terms first, second, third,etc., may be used herein to describe various elements, components,regions, layers and/or sections, these elements, components, regions,layers and/or sections should not be limited by these terms. These termsare only used to distinguish one element, component, region, layer orsection from another element, component, region, layer or section. Thus,a first element, component, region, layer or section discussed belowcould be termed a second element, component, region, layer or sectionwithout departing from the teachings of the invention.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of the invention. Asused herein, the singular forms “a,” “an” and “the” are intended toinclude the plural forms as well, unless the context clearly indicatesotherwise. It will be further understood that the terms “comprises,”“comprising,” “includes” and/or “including,” when used in thisspecification, specify the presence of stated features, integers,operations, elements, and/or components, but do not preclude thepresence or addition of one or more other features, integers, steps,operations, elements, components, and/or groups thereof. Expressionssuch as “at least one of,” when preceding a list of elements, modify theentire list of elements and do not modify the individual elements of thelist. Further, the use of “may” when describing embodiments of thepresent invention refers to “one or more embodiments of the presentinvention.” Also, the term “exemplary” is intended to refer to anexample or illustration. As used herein, the terms “use,” “using,” and“used” may be considered synonymous with the terms “utilize,”“utilizing,” and “utilized,” respectively.

In the following descriptions, the present disclosure will be describedin detail with reference to exemplary embodiments and comparativeexamples.

FIG. 1 is an exploded perspective view for schematically illustrating aliquid crystal display panel 500 according to an exemplary embodiment ofthe present disclosure.

Referring to FIG. 1, the LCD panel 500 may include a first displaysubstrate 100, a second display substrate 200 spaced apart from andfacing the first display substrate 100, and a liquid crystal layer 300interposed between the first display substrate 100 and the seconddisplay substrate 200. Each of the display substrates 100 and 200includes a display area (I) and a non-display area (II). In the displayarea (I), a plurality of pixels may be defined that is arranged in amatrix. The non-display area (II) may be a perimeter area surroundingthe display area (I).

The liquid crystal layer 300 may include liquid crystal molecules, thedirectors of which are aligned vertically with respect to the displaysubstrates 100 and 200, with a pretilt angle.

FIGS. 2 to 8 are cross-sectional views for illustrating a method formanufacturing the LCD panel 500 shown in FIG. 1 according to theexemplary embodiment of the present disclosure.

Referring to FIG. 2, each of the display substrates 100 and 200 will bedescribed in detail.

In the display area (I) of the first display substrate 100, a pluralityof gate lines extending in a first direction, and a plurality of datalines extending in a second direction perpendicular to the firstdirection may be formed. In each of pixels defined by the gate lines andthe data lines, a pixel electrode 180 may be disposed. The pixelelectrode 180 may receive a data voltage via a thin-film transistorworking as a switching element. A gate electrode 125 of the thin-filmtransistor, i.e., a control terminal may be connected to the gate line,a source electrode 152 thereof, i.e., an input terminal may be connectedto the data line, and a drain electrode 155 thereof, i.e., an outputterminal may be connected to the pixel electrode 180 via a contact. Achannel of the thin-film transistor may be formed as a semiconductorlayer 140. The semiconductor layer 140 may be disposed so that itoverlaps the gate electrode 125. The source electrode 152 may be spacedapart from the drain electrode 155 with the semiconductor layer 140therebetween. The pixel electrode 180, along with a common electrode250, may generate electric field so as to control orientations of liquidcrystal molecules in a liquid crystal layer 300 interposed therebetween.

In the non-display area (II) of the first display substrate 100, adriving unit may be disposed that applies a gate driving signal, a datadriving signal and the like to each pixel in the display area (I).

In the display area (I) of the second display substrate 200, a colorfilter 230 may be formed in each pixel. The color filter 230 may includea red, green or blue color filter 230. The red, green, blue colorfilters 230 may be arranged in a repeated order. At a boundary betweenevery two color filters 230, a shield pattern 220 may be disposed.Further, the shield pattern 220 may be extended to the non-display area(II) of the second display substrate 200. The shield pattern 220 in thenon-display area (II) may be wider than the shield pattern 220 formed ata boundary between the color filters 230. On the front face of thedisplay area (I), a common electrode 250 may be disposed across pixels,as a single piece.

The first display substrate 100 and the second display substrate 200 maybe bonded together with a sealing member 310 made of sealent or thelike. The sealing member 310 may be a perimeter area around the firstdisplay substrate 100 and the second display substrate 200, and may bedisposed in the non-display areas (II).

The first display substrate 100 may have a first substrate 110 as itsbase substrate. The first substrate 110 may include the display area (I)and the non-display area (II). The first substrate 110 may be made of atransparent, insulative substrate such as glass or transparent plastic.

On the first substrate 110 in the display area (I), gate lines made of aconductive material, and gate electrodes 124 protruding from the gatelines are formed. Although not shown in the drawings, the gate lines maybe extended to the non-display area (II) to thereby form gate pads inthe non-display area (II).

The gate lines and the gate electrodes 125 are covered by a gateinsulating film 130. The gate insulating film 130 is extended to thenon-display area (II).

On the gate insulating film 130 in the display area (I), a semiconductorlayer 140 and an ohmic contact layer (not shown) may be formed. On thesemiconductor layer 140 and the ohmic contact layer, a source electrode152 branching off from the data line, and a drain electrode 155 spacedapart from the source electrode 152 may be formed. Although not shown inthe drawings, the data line may be extended to the non-display area (II)to thereby form a data pad in the non-display area (II).

On the source electrode 152 and the drain electrode 155, a passivationfilm 160 may be formed that is a type of insulating film made of aninsulative material, such as silicon nitride film, silicon oxide filmand silicon oxynitride film. On the passivation film 160, an organicfilm 170 made of an organic material made be formed. The passivationfilm 160 and the organic film 170 may be extended to the non-displayarea (II). The passivation film 160 may be eliminated from theconfiguration.

On the organic film 170 in the display area (I), a pixel electrode 180made of a conductive material may be disposed in every pixel. The pixelelectrode 180 may be electrically connected to the drain electrode 155via a contact hole 172 that penetrates the organic film 170 and thepassivation film 160 to expose the drain electrode 155. The pixelelectrode 180 may be made of indium tin oxide, indium zinc oxide, indiumoxide, zinc oxide, tin oxide, gallium oxide, titanium oxide, aluminum,silver, platinum, chrome, molybdenum, tantalum, niobium, zinc,magnesium, an alloy or a stacked film thereof. Although not shown in thedrawings, the pixel electrode 180 may include a slit or an opening inthe display area (I). The slit or opening may be patterned to have apredetermined shape, such as a pattern of islands, sprites or fishbones.

Subsequently, the second display substrate 200 will be described. Thesecond display substrate 200 may have a second substrate 210 as its basesubstrate. The second substrate 210 may be made of a transparent,insulative substrate such as glass or transparent plastic.

On the second substrate 210, a shield pattern 220 is formed. The shieldpattern 220 may be extended to the non-display area (II).

On the shield pattern 220 in the display area (I), a color filter 230may be formed.

On the color filter 230 and the shield pattern 220, an overcoat layer240 may be formed. The overcoat layer 240 may be extended to thenon-display area (II).

On the overcoat layer 240, the common electrode 250 may be disposed. Thecommon electrode 250 may be made of indium tin oxide, indium zinc oxide,indium oxide, zinc oxide, tin oxide, gallium oxide, titanium oxide,aluminum, silver, platinum, chrome, molybdenum, tantalum, niobium, zinc,magnesium, an alloy or a stacked film thereof.

The common electrode 250 may be formed to cover the entirety of thedisplay area (I). Although not shown in the drawings, the commonelectrode 250 may include a slit or an opening in the display area (I).The slit or opening may be patterned to have a predetermined shape, suchas a pattern of islands, sprites or fish bones.

The common electrode 250 may be formed on a part of the non-display area(II) but is not formed at the edge of the second display substrate 200,so that the overcoat layer 240 may be exposed.

In the non-display area (II) of the LCD panel 500, the sealing member310 made of a sealent or the like is formed. The sealing member 310 isformed along the edge of the display area (I) to surround the displayarea (I). Accordingly, the first display substrate 100 and the seconddisplay substrate 200 are bonded together by the sealing member 310, anda cell gap can be defined therebetween. The first display substrate 100and the second display substrate 200 are disposed facing each other withthe cell gap therebetween.

The first display substrate 100 and the second display substrate 200 maybe bonded together by way of placing the pixel electrode 180 of thefirst display substrate 100 and the common electrode 250 of the seconddisplay substrate 200 such that they face each other and then bondingthem with the sealing member 310 made of a sealent or the like.

Referring to FIG. 3, with no electric field applied, a liquid crystalcomposition containing liquid crystal molecules 301 andphotopolymerizable monomer compound 302 for forming liquid crystalalignment films is injected into the cell gap, to form the liquidcrystal layer 300. In doing so, the sealing member 310 can prevent theliquid crystal molecules 310 and the photopolymerizable monomercomposition 302 from leaking out of the cell gap.

On the other hand, the liquid crystal composition may be dropped ontothe first display substrate 100 and the second display substrate 200 invacuum to form the liquid crystal layer 300, and then the first displaysubstrate 100 and the second display substrate 200 may be bondedtogether by way of placing the pixel electrode 180 of the first displaysubstrate 100 and the common electrode 250 of the second displaysubstrate 200 such that they face each other and then bonding them withthe sealing member 310 made of a sealent or the like.

The liquid crystal molecules 301 are in a random planar state, since thesurfaces of the first and second display substrates 100 and 200 have notbeen subjected to any alignment process.

The type of the liquid crystal molecules 310 is not specifically limitedas long as it can be employed in LCD panels. In a non-limiting example,the liquid crystal molecules 301 may be of nematic liquid crystal havingnegative dielectric anisotropy.

The photopolymerizable monomer composition 302 includesphotopolymerizable hydrocarbon derivative having perfluorocarbon groupor a mixture thereof, and a mixture of photopolymerizable hydrocarbonderivative having perfluorocarbon group and hydrocarbon derivativehaving photopolymerization reactive group.

The hydrocarbon derivative having perfluorocarbon group includesphotopolymerization reactive group. The perfluorocarbon group includesperfluoroalkyl group having 1 to 50 carbon atoms and perfluoroalkoxygroup having 1 to 50 carbon atoms. The photopolymerization reactivegroup may be, but is not limited to, (meth)acryloyl group.

The photopolymerizable hydrocarbon derivative having perfluorocarbongroup may be, but is not limited to, a compound represented bystructural formulas below, or a mixture thereof.

where a is 0 or 1, n is a natural number from 1 to 11, and A isphotopolymerization reactive group.

where a is 0 or 1, n₃ is a natural number from 1 to 10, and A isphotopolymerization reactive group.

where a is zero or 1, n₄ is a natural number from 1 to 6, and A isphotopolymerization reactive group.

where a is 0 or 1, n₅ and n₆ are natural numbers from 1 to 6,respectively, and A is photopolymerization reactive group.

In a non-limiting example, a mixture of photopolymerizable hydrocarbonderivative having perfluorocarbon group may be a mixture of one or moreof compounds represented by Formula 1 that has one photopolymerizationreactive group, and one or more of compounds represented by Formula 2 to4 that has two photopolymerization reactive groups. In this regard, themixture may contain one of the compounds represented by Formula 1 andone of the compounds represented by Formulas 2 to 4 of at least 1 weight%, respectively, with respect to the total weight of the mixture.

The hydrocarbon derivative having polymerization reactive group may be,but is not limited to, a compound represented by Formula 5 below. Thephotopolymerization reactive group may be, but is not limited to,(meth)acryloyl group.

where n is a natural number from 6 to 26, and A is photopolymerizationreactive group.

In Formula 5, it is advantageous to use a compound in which n is equalto or larger than 6 since the vertical alignment of the liquid crystalmolecules 310 by the polymerization could not be effectively conductedif n is less than 6. Further, it is desired to use a compound in which nis equal to or larger than 10 since the vertical alignment of the liquidcrystal molecules 301 is more thermally-stable as n is larger.Therefore, n may be a natural number, preferably, from 10 to 26.

In a non-limiting example, the mixture of photopolymerizable hydrocarbonderivative having perfluorocarbon group and hydrocarbon derivativehaving photopolymerization reactive group may be a mixture of one ormore photopolymerizable hydrocarbon derivative having perfluorocarbongroup selected from the compounds represented by Formulas 2 to 4 andhydrocarbon derivative having photopolymerization reactive grouprepresented by Formula 5. The hydrocarbon derivative havingphotopolymerization reactive group may be added with the weight fractionof 10 part by weight to 70 part by weight with respect to the totalweight of the photopolymerizable hydrocarbon derivative havingperfluorocarbon group.

The liquid crystal composition may further include typicalphoto-initiator for inducing photopolymerization reaction of thephotopolymerizable monomer compound 302.

If the content of the photopolymerizable monomer compound 302 containedin the liquid crystal composition is too low, the effects of verticalalignment of the liquid crystal molecules 301 and stabilization oforientation are insignificant. On the contrary, the content of thephotopolymerizable monomer compound 302 is too high, bad orientation maybe caused by high density and the performance of the LCD device may bedeteriorated since it may be overly stabilized.

Accordingly, the weight fraction of the photopolymerizable monomercompound 302 with respect to the total weight of the liquid crystalcomposition may range from 0.05 wt % to 5 wt %, from 0.1 wt % to 3 wt %,or from 0.2 wt % to 2 wt %.

In some instances, a process for uniformizing the liquid crystalcomposition may optionally be carried out after injection of the liquidcrystal composition, involving heating the LCD panel 500 at atemperature higher than the nematic-isotropic phase transitiontemperature of the liquid crystal molecules 301 and photopolymerizablemonomer compound 302 by 0.1° C. to 20° C. and then cooling down it. Inparticular, the heating may be carried out at a heating rate of 5 to 10°C./min up to a temperature higher than an isotropic phase transitiontemperature of liquid crystals by 0.1° C. to 20° C. in 1 second to 5minutes, and cooling was carried out at a rate of 5 to 10° C./min downto room temperature.

Referring to FIG. 4, the LCD panel 500 having the liquid crystal layer300 formed between the first display substrate 100 and the seconddisplay substrate 200, with no electric field applied thereto, may beirradiated with UV ray, so that the liquid crystal molecules 301 arevertically aligned. Hereinafter, the UV irradiation is referred to as afirst light irradiation.

The UV ray may have a wavelength to allow photopolymerization reactionto occur and may have, but is not limited to, a wavelength from 250 nmto 450 nm. The wavelength to allow photopolymerization reaction to occurmay vary depending on the structure of the photopolymerizable monomercompound 302. The UV ray may be perpendicularly incident on the displaysubstrates 100 and 200 and is may not be polarized.

The light intensity, irradiation time and temperature appropriate forinducing vertical alignment of the liquid crystal molecules 301 may varydepending on chemical structure and concentration of thephotopolymerizable monomer compound 302, solubility for the liquidcrystal molecules 301, and the number and reactivity of thephotopolymerization reactive group.

For example, when the concentration of the photopolymerizable monomercompound 302 with respect to the total weigh of the liquid crystalcomposition is between 0.05 wt % and 5 wt %, the LCD panel may beirradiated with UV ray with intensity of several hundreds mW/cm² toseveral tens μW/cm² for 1 minute to 2 hours, thereby reducing verticalalignment of the liquid crystal molecules 301.

It is noted that the effective irradiation time given above is notlimiting but may vary depending on the concentration of thephotopolymerizable monomer compound 302 and the light intensity.

The UV irradiation may be carried out on a condition that the liquidcrystal layer 300 disposed between the two display substrates 100 and200 exhibits liquid crystal phase or isotropic phase, preferably on thecondition that it exhibits the isotropic phase. Accordingly, it may bemore efficient for inducing the vertical alignment of the liquid crystalmolecules 301 to perform light irradiation while heating the liquidcrystal layer 300.

Referring to FIG. 5, as in FIG. 4, with no electric field applied, theliquid crystal layer 300 was irradiated with UV irradiation. As aresult, the photopolymerizable monomer compound 302 is polymerized andis phase-separated from the liquid crystal molecules 301, and isconcentrated on the surfaces of the respective display substrates 100and 200, to form liquid-crystal vertical-alignment layers 190 and 270 asrigid solid thin-films. The concentration of the photopolymerizablemonomer compound 302 in the liquid crystal composition is reduced by thefirst light irradiation.

The liquid crystal molecules 301 are aligned vertically to the displaysubstrates 100 and 200, so that vertical orientation is achieved inwhich the average director and optical axis of the liquid crystalmolecules 301 are aligned vertically to the display substrates 100 and200.

The liquid crystal layer 300 subjected to the light irradiation wasobserved with a polarizing microscope. As a result, it could be seenthat vertical alignment of the liquid crystal molecules 301 was induceduniformly to exhibit a dark state through the crossed polarizers. Inaddition, by using the conoscopy technique, it could be seen that theoptical axis of the liquid crystal layer 300 is aligned vertically tothe display substrates 100 and 200.

Then, electric field is applied to the vertically-aligned, liquidcrystal layer 300, to evaluate electro-optical switching properties.

As described above, in the vertical orientation of the liquid crystalmolecules 301 induced by the first light irradiation, the liquid crystalmolecules 301 do not have a pretilt angle in a particular direction.When electric field perpendicular to the display substrates 100 and 200is applied to the LCD panel 300 via the pixel electrode 180 and thecommon electrode 250, the liquid crystal molecules 301 rotate in thedirection perpendicular to the electric field to thereby increase thetransmittance. At this time, since the liquid crystal molecules 301 donot have a pretilt angle in a particular direction, the rotationdirections of the liquid crystal molecules 301 differ from location tolocation in the liquid crystal layer 300. Consequently, defects in theorientation of the liquid crystal molecules 301 occur, causing theproperties of the LCD panel 500 to deteriorate.

Referring to FIG. 6, with electric field applied, the liquid crystallayer 300 is irradiated with UV ray to induce the liquid crystalmolecules 301 to have a particular pretilt angle. Hereinafter, this UVirradiation is referred to as a second light irradiation.

The process of applying electric field may be carried out under thecondition that a DC or AC electric field is applied such that the lighttransmittance of the LCD panel 500 is 5% (T05) to 100% (T100) of themaximum transmittance through the crossed polarizers.

By applying electric field under the above condition, a particularoptical state is induced for the liquid crystal molecules 301 in theliquid crystal display panel 500, and the photopolymerizable monomercompound 302 chemically reacts additionally, thereby achieving surfacestabilization of the pretilt angle of the liquid crystal molecules 301.

At this time, the UV ray used may have a wavelength, preferably, rangingfrom 300 nm to 400 nm. It is preferable to irradiate with the UV raywith intensity from 200 mW/cm² to 50 μW/cm² for 1 minute to 60 minutes,in that the light stabilization efficiency of the photopolymerizationreactive group of the photopolymerizable monomer compound 302 ismaximized to achieve the surface stabilization of the orientation of theliquid crystal molecules 301.

It is preferable to apply electric field and wait until after defectsare minimized, and then to perform the process of UV irradiation afterthe orientation of the liquid crystal molecules 301 is stabilized.Further, the process of UV irradiation may be carried out as two or moresub-steps with different intensities of electric field or UV ray.

The ranges of UV rays used in the first light irradiation and the secondlight irradiation may be individually selected so that they may or maynot overlap each other depending on the photopolymerization reactivegroup of the photopolymerizable monomer compound 302 used.

It is preferable to carry out the second UV irradiation on a conditionthat the liquid crystal layer 300 disposed between the two displaysubstrates 100 and 200 exhibits a liquid crystal phase. Since the lightirradiation can be carried out while the orientation of the liquidcrystal molecules 301 is controlled in a particular state with theapplied voltage, it is more efficient to stabilize orientation than inthe isotropic phase.

Referring to FIG. 7, by virtue of the second light irradiation, thephotopolymerizable monomer compound 302 in the liquid crystal layer 300forms polymer, and the liquid-crystal vertical-alignment layers 190 and270 are modified as alignment stabilization layers 190′ and 270′ formaking a pretilt angle of the liquid crystal molecules 301. At thistime, the liquid crystal molecules 301 are inclined with respect to thedisplay substrates 100 and 200 by the electric field applied. In someinstances, the liquid crystal molecules 301 may be parallel to thedisplay substrates 100 and 200 by the electric field applied.

Referring to FIG. 8, the electric field is removed after the alignmentstabilization layers 190′ and 270′ are formed, and the liquid crystalmolecules 301 transition to a vertical orientation state memorizing thepretilt direction.

Thus far, the two-step light irradiation has been described, in whichthe first light irradiation is carried out with no electric fieldapplied so as to induce the vertical alignment of the liquid crystalmolecules 301 and then the second irradiation is carried out withelectric field applied so as to stabilize the pretilt angle of theliquid crystal molecules 301. However, it is also possible to induce thevertical alignment of the liquid crystal molecules 301 and stabilize thepretilt angle of the liquid crystal molecules 301 by carrying out lightirradiation once, with electric field applied from the beginning,instead of two-step irradiation.

More detailed description on this will be made below with reference toFIGS. 9 to 12.

Referring to FIG. 9, even when electric field is applied after theliquid crystal layer 300 is formed between the two display substrates100 and 200, the liquid crystal molecules 301 do not react with theelectric field applied due to the negative dielectric anisotropy of theliquid crystal molecules 301. Thus, the liquid crystal molecules 301 arearranged parallel to the surfaces of the two display substrates 100 and200, i.e., in a random planar state like in FIG. 3.

Referring to FIGS. 10 and 11, when the LCD panel 500 is irradiated withUV ray with electric field applied, photopolymer created from thephotopolymerizable monomer compound 302 forms liquid-crystalvertical-alignment films 190 and 270 for inducing vertical alignment ofthe liquid crystal molecules 301 on the surfaces of the pixel electrode180 and the common electrode 250. The liquid crystal molecules 301 havethe arrangement inclined toward a particular direction in response toelectric field applied.

The inclination degree of the liquid crystal molecules 301 depends onthe level of the voltage applied. Depending on the state of the liquidcrystal molecules 301 to be stabilized, a voltage may be applied thathas the level corresponding to the transmittance between 5% and 100%through the crossed polarizers.

Accordingly, it is possible to carry out the process with two or morevoltages or light intensities while varying intensity of electric fieldapplied or light for irradiation, during the process of lightirradiation.

FIG. 12 show a process in which light irradiation is carried outcontinuously onto the LCD panel 500.

The light irradiation may be carried out at a temperature within therange of the nematic phase temperature of the liquid crystalcomposition. After the light irradiation, an additional process ofheating the produced liquid crystal layer 300 above the isotropictransition temperature and then cooling it down may be carried out. Suchlight irradiation method has been described above with reference toFIGS. 2 to 8.

Forming the alignment stabilization layers 190′ and 270′ and verticallyaligning the pretilted liquid crystal molecules 301 are the same asdescribed above with respect to FIGS. 7 and 8.

Although not shown in FIGS. 2 to 12, if the pixel electrode 180 and/orthe common electrode 250 are micro-slit-patterned in every pixel, thepretilt angle of the liquid crystal molecules 301 in multiple domainscan be stabilized in every pixel.

When the LCD panel 500 is manufactured according to the method ofinducing and stabilizing orientation of liquid crystals byphotopolymerization chemical reaction of photopolymerizable monomercomposition 302, viewing angle, brightness and contrast ratio of the LCDpanel 500 can be improved and the switching speed of liquid crystalmolecules can be faster.

Since the method is carried out at room temperature or at around theisotropic phase temperature of the liquid crystal molecules 301, theprocess temperature is low and the processes is simple, so that themethod can replace traditional alignment film coating process and firingprocess carried out at high temperature. Accordingly, in addition tohigh definition LCD devices employing glass substrates, the method isuseful in manufacturing display devices vulnerable to high-temperatureprocesses, such as flexible LCD display panel, since the method does notinvolve the alignment film firing process carried out athigh-temperature.

The LCD panel manufactured according to the method of the presentdisclosure may be applicable to a variety of electro-optical devicesusing liquid crystal molecules, such as TVs, 3D-TV, monitors, tabletPCs, various types of mobile devices, and particularly flat paneldisplays.

[First Embodiment]

An LCD panel was manufactured using, as first and second displaysubstrates, display substrates on which unpatterned, transparentelectrodes (ITO) are formed, according to the method described abovewith reference to FIGS. 2 to 8.

Unpatterned, transparent electrodes (ITO) were formed on the first andsecond display substrates, respectively. Subsequently, ultrasoniccleaning is performed on them in distilled water using a cleaning agent,then they were cleaned using acetone and isopropyl alcohol,respectively, and were dried.

The first display substrate and the second display substrate wereassembled such that the transparent electrodes thereon face each other,without any alignment process. A composition for forming a liquidcrystal layer was produced with the weight fraction of 99.0 wt % ofliquid crystal molecules having negative dielectric anisotropy, and 1.0wt % of a mixture of photopolymerizable monomer compound andphoto-initiator having 2.0 wt % with respect to the photopolymerizablemonomer compound, the photopolymerizable monomer compound is produced bymixing 50 wt % of a compound represented by Formula 1-1 below, and 50 wt% of a compound represented by Formula 2, where n₂ is 7. The LCD panelassembly was manufactured by injecting the composition for forming aliquid crystal layer thereinto. In Formulas 1-1 and 2 below, A-groupdenotes photopolymerizable acryloyl group.

where a is 1, and n₂ is 3, 5, 7 or 9.

where a is 0, and n₃ is 4.

In making an LCD panel assembly, the distance between the first displaysubstrate and the second display substrate was maintained to be 10 μm.The process of injecting the composition for forming a liquid crystallayer was carried out at 95° C., which is the isotropic-phasetemperature of the composition.

After the injection of the composition, the LCD panel assembly wascooled down at room temperature, and the orientation of the liquidcrystal molecules was observed with a polarizing microscope.

As a result, it was observed that the liquid crystal molecules in theliquid crystal layer were randomly arranged in the horizontal directionwith respect to the display substrates, due to the surfaces notsubjected to any alignment process, as shown in FIG. 13.

Subsequently, the LCD panel assembly was heated at 92° C., which is theisotropic-phase temperature of the composition for forming a liquidcrystal layer. Then, with no electric field applied to the LCD panelassembly, it was irradiated with ultraviolet (UV) ray (wavelength of 365nm, the intensity of 2 mW/cm²) for 10 minutes, so that thephotopolymerizable monomer compound, which was mixed with the liquidcrystal molecules at the time of forming the liquid crystal layer,reacts with the UV ray, inducing vertical alignment of the liquidcrystal molecules.

The LCD panel thus manufactured was observed with a polarizingmicroscope at room temperature, and the result can be seen from FIG. 14.In addition, the orientation of the liquid crystal molecules wasobserved using a conoscopy image, and the result can be seen from FIG.15.

As can be seen from FIG. 14, in the manufactured LCD panel, the liquidcrystal layer exhibited a completely dark state through the crossedpolarizers. Further, as can be seen from the conoscopy image shown inFIG. 15, the liquid crystal molecules were aligned vertically withrespect to the surfaces of the substrates.

During the processes of manufacturing the LCD panel illustrated in FIGS.2 to 8, electric field corresponding to the voltage level of 5 V wasapplied to the LCD panel assembly in which liquid crystal molecules arevertically aligned with the first light irradiation, and the orientationof the liquid crystal molecules was observed. The results before andafter applying the electric field are shown in FIGS. 16 to 18,respectively.

Typically, a liquid crystal layer having liquid crystal moleculesvertically aligned with respect to display substrates exhibits a darkstate through crossed polarizers as shown in FIG. 16. When an electricfield is applied thereto, the liquid crystal molecules rotate in thedirection perpendicular to the electric field and, accordingly,transmittance is increased as is evidenced by FIG. 16. If the liquidcrystal molecules are not pretilted toward a particular direction,however, the liquid crystals rotate in random directions in the liquidcrystal cell. Accordingly, a number of defects occur in orientation ofthe liquid crystals as shown in FIG. 17, deteriorating characteristicsof the LCD device. However, the defects shown in FIG. 17 disappearslowly with time, and a transition is made to a bright state with fewerdefects as shown in FIG. 18.

Subsequently, an AC electric field of T80 (transmittance of 80% relativeto the maximum transmittance) was applied across the first and seconddisplay substrates of the LCD panel thus manufactured at roomtemperature, to see that defects were minimized and the orientation ofthe liquid crystal molecules was stabilized. Then, the LCD panel withelectric field applied thereto was irradiated with UV ray (thewavelength of 365 nm, the intensity of 20 mW/cm²) for 30 minutes, sothat, among photopolymerizable monomer compounds mixed with the liquidcrystal molecules at the time of forming the liquid crystal layer, thosenot photo-polymerized with the first light irradiation arephoto-polymerized, thereby inducing a pretilt angle of the liquidcrystal molecules and stabilizing the surfaces to manufacture the LCDpanel.

The LCD panel thus manufactured was observed with a polarizingmicroscope, and it was seen that the liquid crystal layer, with noelectric field applied thereto, exhibited a complete dark state throughthe crossed polarizers, like before the second light irradiation.

In addition, observation was made on the final LCD panel manufactured byapplying electric field to and performing the second light irradiationon the LCD panel assembly manufactured according to the firstembodiment, to see if defects in the liquid crystal molecules occur atthe time of switching on/off the device. The results can be seen fromFIGS. 19 and 20.

Upon applying electric field corresponding to the voltage level of 5 Vagain in a dark or black state as shown in FIG. 19, it was observed thatthe liquid crystal molecules reacted with the electric field to changethe orientation. Accordingly, the optical axis of the liquid crystalmolecules made the angle of 45 degree with the transmission axes of thepolarizers on the surfaces of the respective display substrates, so thatthe transition to a bright state was made as shown in FIG. 20 withoutcausing defects of the liquid crystal molecules.

This is resulted from a series of processes that the photopolymerizablemonomer compound in the liquid crystal composition forms somephotopolymer by the first light irradiation to thereby induce verticalalignment on the surfaces of the display substrates, and the polymercreated from the residual photopolymerizable monomer compound, which hasnot reacted, form the alignment stabilization layer during the secondlight irradiation to thereby stabilize the pretilt angle of the liquidcrystal molecules induced by electric field.

The same experiment as that in the first embodiment was carried outusing a photopolymerizable monomer compound represented by Formula 1-1with a different value for n₂, a result of which is shown in Table 1:

TABLE 1 Initial LC Molecules n₂ Orientation Before Orientation AfterPretilt value Light Irradiation Irradiation Stabilization 3 HorizontalVertical Yes 5 Horizontal Vertical Yes 7 Horizontal Vertical Yes 9Horizontal Vertical Yes

As can be seen from Table 1, the initial, random planar state istransitioned to a vertical orientation as the photopolymerizable monomercompounds are polymerized by light irradiation, and the pretilt angle isstabilized in a particular direction, so that the response time of theLCD panel becomes faster and the brightness and contrast ratio of thedevice are improved.

[Second Embodiment]

The substrates were manufactured and bonded to each other and the liquidcrystal composition was injected in the same method as that in the firstembodiment, except for that the liquid crystal composition was producedusing 0.7 wt % of a compound represented by Formula 2 as thephotopolymerizable monomer compound, where n₃ is 6, and 99.3 wt % ofliquid crystal molecules having negative dielectric anisotropy. Thephoto-initiator was mixed with the photopolymerizable monomer compoundwith the same weight fraction. In Formula 2, A-group denotesphotopolymerizable acryloyl group.

where a is 0, and n₃ is 2, 4, 6 or 8.

After the injection of the composition, the LCD panel assembly wascooled down at room temperature, and the orientation of the liquidcrystal molecules was observed with a polarizing microscope. As aresult, like in the first embodiment, it was observed that the liquidcrystal molecules in the liquid crystal molecule cells were randomlyarranged in the horizontal direction with respect to the substrates, dueto the surfaces not subjected to any alignment process.

Subsequently, electric field was applied to the LCD panel assembly, andit was seen that the liquid crystal molecules do not react with theelectric field applied due to negative dielectric anisotropy of theliquid crystal molecules and thus they remain in the initial, randomplanar state.

The LCD panel, with electric field applied thereto, was irradiated withultraviolet (UV) ray (wavelength of 365 nm, the intensity of 2 mW/cm²)for 30 minutes, and then with UV ray (intensity of 20 mW/cm²) for 30minutes at room temperature, so that the photopolymerizable monomercompound, which was mixed with the liquid crystal molecules at the timeof forming the liquid crystal layer, reacted with the UV ray, inducingvertical alignment of the liquid crystal molecules and stabilizing it.

After removing the electric field and heating the LCD panel up to 95° C.to cool it down, the LCD panel thus manufactured was observed with apolarizing microscope at room temperature, and the result can be seenfrom FIG. 21. As can be seen from FIG. 21, in the LCD panel thusmanufactured, the liquid crystal layer exhibited a completely dark statethrough the crossed polarizers, and the liquid crystal molecules werealigned vertically with respect to the surfaces of the substrates.

Electric field corresponding to the voltage level of 4 V was applied tothe LCD panel and it was observed whether defects occur in the liquidcrystal molecules at the time of switching on/off the device. Theresults before and after applying electric field are shown in FIGS. 21and 22, respectively.

Upon applying electric field corresponding to the voltage level of 4V inan initial dark state as shown in FIG. 21, it was observed that theliquid crystal molecules reacted with the electric field to change theorientation. Accordingly, the optical axis of the liquid crystalmolecules made the angle of 45 degree with the transmission axes of thepolarizers on the surfaces of the respective display substrates, so thatthat the transition to a bright state was made as shown in FIG. 22without causing defects of the liquid crystal molecules.

This is resulted from a series of processes that the photopolymerizablemonomer compound in the liquid crystal composition forms somephotopolymer by the initial light irradiation to thereby induce verticalalignment on the surfaces of the display substrates, so that the liquidcrystal molecules react with the electric filed to be inclined, and thepolymer created from the residual photopolymerizable monomer compound,which has not reacted, form the alignment stabilization layer during thecontinued light irradiation to thereby stabilize the pretilt angle ofthe liquid crystal molecules induced by electric field.

The same experiment as that in the second embodiment was carried outusing a photopolymerizable monomer compound represented by Formula 2with a different value for n₃, a result of which is shown in Table 2:

TABLE 2 Initial Liquid Crystal n₃ Orientation Before Orientation AfterPretilt value Irradiation Irradiation Stabilization 2 HorizontalVertical Yes 4 Horizontal Vertical Yes 6 Horizontal Vertical Yes 8Horizontal Vertical Yes

As can be seen from Table 2, the initial, random planar state istransitioned to a vertical orientation as the photopolymerizable monomercompounds are photo-polymerized by light irradiation, and the pretiltangle is stabilized in a particular direction, so that the response timeof the LCD panel becomes faster and the brightness and contrast ratio ofthe device are improved.

[Third Embodiment]

The LCD panel was manufacture according to the same method as in thefirst embodiment and evaluated the orientation of the liquid crystalmolecules and switching characteristics of the device, except for thatthe LCD panel assembly was manufactured by injecting a composition forforming a liquid crystal layer thereinto, the composition for forming aliquid crystal layer being produced with the weight fraction of 99.0 wt% of liquid crystal molecules having negative dielectric anisotropy, and1.0 wt % of a mixture of photopolymerizable monomer compound andphoto-initiator having 2.0 wt % with respect to the photopolymerizablemonomer compound, the photopolymerizable monomer compound being producedby mixing 50 wt % of a compound represented by Formula 1-1, and 50 wt %of a compound represented by Formula 3, where n is 7. In Formulas 1-1and 3 below, A-group denotes photopolymerizable methacryl group or acrylgroup, respectively.

where a is 1, and n₂ is 3, 5, 7 or 9.

where a is 0, and n₄ is 3.

The LCD panel thus manufactured was observed with a polarizingmicroscope, and it was seen that the liquid crystal layer, with noelectric field applied thereto, exhibited a complete dark state throughthe crossed polarizers.

Additionally, it was observed whether defects occur in the liquidcrystal molecules at the time of switching on/off the LCD display devicemanufactured in the third embodiment, and, as a result, it was seen thatthe transition to a bright state was made without causing defects of theliquid crystal molecules.

The same experiment as that in the third embodiment was carried outusing a photopolymerizable monomer compound represented by Formula 1-1with a different value for n₂, a result of which is shown in Table 3:

TABLE 3 Initial Liquid Crystal Orientation Before Orientation AfterPretilt n₂ Irradiation Irradiation Stabilization 3 Horizontal VerticalYes 5 Horizontal Vertical Yes 7 Horizontal Vertical Yes 9 HorizontalVertical Yes

As can be seen from Table 3, the initial, random planar state istransitioned to a vertical orientation as the monomer compounds arephoto-polymerized by light irradiation, and the pretilt angle isstabilized in a particular direction, so that the response time of theLCD panel becomes faster and the brightness and contrast ratio of thedevice are improved.

[Fourth Embodiment]

The LCD panel was manufacture according to the same method as in thefirst embodiment and evaluated the orientation of the liquid crystalmolecules and switching characteristics of the device, except for thatthe LCD panel assembly was manufactured by injecting a composition forforming a liquid crystal layer thereinto, the composition for forming aliquid crystal layer being produced with the weight fraction of 99.0 wt% of liquid crystal host having negative dielectric anisotropy, and 5 wt% of a mixture of photopolymerizable monomer compound andphoto-initiator having 2.0 wt % with respect to the photopolymerizablemonomer compound, the photopolymerizable monomer compound being producedby mixing 50 wt % of a compound represented by Formula 5, and 50 wt % ofa compound represented by Formula 3, where n is 18. In formulas below,A-group denotes photopolymerizable acryloyl group.

where n is 6, 10, 14, 18 or 22

where a is 0, and n₄ is 3.

The LCD panel thus manufactured was observed with a polarizingmicroscope, and it was seen that the liquid crystal layer, with noelectric field applied thereto, exhibited a complete dark state throughthe crossed polarizers.

Additionally, it was observed whether defects occur in the liquidcrystal molecules at the time of switching on/off the LCD display devicemanufactured in the fourth embodiment, and, as a result, it was seenthat the transition to a bright state was made without causing defectsof the liquid crystal molecules. The results can be seen from FIGS. 23and 24.

Upon applying electric field corresponding to the voltage level of 3V inan initial dark state as shown in FIG. 23, it was observed that theliquid crystal molecules reacted with the electric field to change theorientation. Accordingly, the optical axis of the liquid crystalmolecules made the angle of 45 degree with the transmission axes of thepolarizers on the surfaces of the respective display substrate, so thatthat the transition to a bright state was made as shown in FIG. 24without causing defects of the liquid crystal molecules.

Further, the orientation of the liquid crystal molecules according totemperature change was observed while heating the sample in which theliquid crystal molecules are vertically aligned at room temperature. Asa result, transition to the horizontal orientation was observed at about89° C. to 89.5° C., and the transition to isotropic phase was completedat 90° C.

The same experiment as that in the forth embodiment was carried outusing a photopolymerizable monomer compound represented by Formula 5with a different value for n, a result of which is shown in Table 4:

TABLE 4 Initial LC Molecules Orientation Orientation OrientationTransition n Before After Temperature Pretilt value IrradiationIrradiation (° C.) Stabilization 4 Horizontal Horizontal — No 8Horizontal Vertical 39~40 Yes 10 Horizontal Vertical 58~60 Yes 14Horizontal Vertical 70~72 Yes 18 Horizontal Vertical  89~89.5 Yes 22Horizontal Vertical  89~89.5 Yes

As can be seen from Table 4, although vertical alignment was not inducedfor the compound where n is 4, for the compound where n is equal to orlarger than 8, the initial, random planar state is transitioned to avertical orientation as the monomer compounds are photo-polymerized bylight irradiation, and the pretilt angle is stabilized in a particulardirection, so that the response time of the LCD panel becomes faster andthe brightness and contrast ratio of the device are improved. It couldalso be seen that the orientation transition temperature from thevertical to horizontal orientation after irradiation increases with thevalue for n. This represents temperature stability of the verticalorientation. In other words, it can be seen that the orientation is morestable as the chain length of a compound represented by Formula 5increases. The isotropic-nematic phase transition temperature of thehost liquid crystal molecules used is 90.0° C.

[Fifth Embodiment]

The LCD panel was manufacture according to the same method as in thefirst embodiment and evaluated the orientation of the liquid crystalmolecules and switching characteristics of the device, except for thatthe LCD panel assembly was manufactured by injecting a composition forforming a liquid crystal layer thereinto, the composition for forming aliquid crystal layer being produced with the weight fraction of 99.0 wt% of liquid crystal host having negative dielectric anisotropy, and 5 wt% of a mixture of photopolymerizable monomer compound andphoto-initiator having 2.0 wt % with respect to the photopolymerizablemonomer compound, the photopolymerizable monomer compound being producedby mixing 50 wt % of a compound represented by Formula 5, and 50 wt % ofa compound represented by Formula 2, where n is 22. In formulas below,A-group denotes photopolymerizable acryloyl group.

where n is 6, 10, 14, 18 or 22

where a is 0, and n₃ is 6.

The LCD panel thus manufactured was observed with a polarizingmicroscope, and it was seen that the liquid crystal layer, with noelectric field applied thereto, exhibited a complete dark state throughthe crossed polarizers. FIG. 25 is a photograph of the LCD panel thusmanufacture taken through the crossed polarizers; and FIG. 26 is aphotograph taken with a polarizing microscope.

Additionally, it was observed whether defects occur in the liquidcrystal molecules at the time of switching on/off the LCD display devicemanufactured in the fifth embodiment, and, as a result, it was seen thatthe transition to a bright state was made without causing defects of theliquid crystal molecules. The results can be seen from FIGS. 26 and 27.

Upon applying electric field corresponding to the voltage level of 4V inan initial dark state as shown in FIG. 26, it was observed that theliquid crystal molecules reacted with the electric field to change theorientation. Accordingly, the optical axis of the liquid crystalmolecules made the angle of 45 degree with the transmission axes of thepolarizers on the surfaces of the respective display substrate, so thatthat the transition to a bright state was made as shown in FIG. 27without causing defects of the liquid crystal molecules.

The same experiment as that in the forth embodiment was carried outusing a photopolymerizable monomer compound represented by Formula 5with a different value for n, a result of which is shown in Table 4:

TABLE 5 Initial LC Molecules Orientation Orientation OrientationTransition n Before After Light Temperature Pretilt value IrradiationIrradiation (° C.) Stabilization 4 Horizontal Horizontal — No 8Horizontal Vertical 40~45 Yes 10 Horizontal Vertical 60~63 Yes 14Horizontal Vertical 72~75 Yes 18 Horizontal Vertical  89~89.5 Yes 22Horizontal Vertical  89~89.5 Yes

As can be seen from Table 5, for the photopolymerizable monomer compoundwhere n is 8 to 22, the initial, random planar state is transitioned toa vertical orientation as the monomer compounds are photo-polymerized bylight irradiation, and the pretilt angle is stabilized in a particulardirection, so that the response time of the LCD panel becomes faster andthe brightness and contrast ratio of the device are improved.

[Sixth Embodiment]

An IZO (Indium Zinc Oxide) electrode, which has a micro-slit pattern offish bones, was used as a pixel electrode in every pixel, while anunpatterned IZO electrode was used as a common electrode, so that theupper substrate are bonded to the lower substrate with the distance ofabout 4 μm therebetween, and a liquid crystal composition containingphotopolymerizable monomer compound was injected in the same manner asthat in the first embodiment without any alignment process.

A mixture was used as the liquid crystal composition, in which 99.0 wt %of liquid crystal host having negative dielectric anisotropy, and 1 wt %of a mixture of photopolymerizable monomer compound and photo-initiatorhaving 2.0 wt % with respect to the photopolymerizable monomer compoundwere uniformly mixed, the photopolymerizable monomer compound beingproduced by mixing 50 wt % of a compound represented by Formula 5, and50 wt % of a compound represented by Formula 2, where n is 18.

Light irradiation was carried out in the same manner as in the firstembodiment to manufacture an LCD panel, and orientation of the liquidcrystal molecules and switching characteristic were evaluated.

After the injection of the liquid crystal composition, the orientationof the liquid crystal molecules in the device was observed with apolarizing microscope while rotating the sample before lightirradiation. As a result, it was seen that the liquid crystal moleculeswere not vertically aligned. In this instance, the liquid crystalmolecules exhibited a random planar state as shown in FIG. 28.

As a result of observing the LCD panel subjected to the first and secondlight irradiation with a polarizing microscope, it was seen that theliquid crystal layer of the LCD panel exhibited a completely dark statethrough the crossed polarizers as shown in FIG. 29. Further, as can beseen from the conoscopy image shown in FIG. 30, the liquid crystalmolecules were aligned vertically with respect to the surfaces of thesubstrates.

In addition, an electric field of T80 (transmittance of 80% relative tothe maximum transmittance) was applied to the LCD panel, and then theorientation of the liquid crystal molecules was observed. In this case,in a pixel divided into four domains with electrodes having a micro-slit(branch) pattern, it was observed that transition was made quickly to auniformly bright state without causing defects.

Upon applying electric field of T80 (transmittance of 80% relative tothe maximum transmittance) in a dark or black state as shown in FIG. 29,it was observed that the liquid crystal molecules reacted with theelectric field to change the orientation. Accordingly, in a pixeldivided into four domains, the optical axis of the liquid crystalmolecules made the angle of 45 degree with the transmission axes of thepolarizers on the surfaces of the respective display substrates, so thatthe transition to a bright state was made quickly without causingdefects of the liquid crystal molecules, as shown in FIGS. 31 and 32.This resulted from the surface stabilization of the orientation of theliquid crystal molecules in such a manner that the liquid crystalmolecules in a pixel make pretilt angles in four different directionseach making 45 degree with the transmission axes of the polarizers. Bydoing so, it was seen that the response speed of the liquid crystalmolecules was improved while the brightness and the contrast ratio ofthe device was enhanced.

While the present invention has been particularly shown and describedwith reference to exemplary embodiments and examples thereof, it will beunderstood by those of ordinary skill in the art that various changes inform and detail may be made therein without departing from the spiritand scope of the present invention as defined by the following claims.The exemplary embodiments should be considered in a descriptive senseonly and not for purposes of limitation.

What is claimed is:
 1. A LCD panel, comprising: substrates facing eachother; a liquid crystal layer disposed between the substrates; andliquid crystal alignment layers, each sandwiched between the liquidcrystal layer and a respective one of the substrates, wherein each ofthe liquid crystal alignment layers comprises a non-polyimidehydrocarbon derivative having a perfluorocarbon group, and the liquidcrystal layer comprises a monomer compound of the non-polyimidehydrocarbon derivative having a perfluorocarbon group.
 2. The LCD panelof claim 1, wherein the perfluorocarbon group is at least one ofperfluoroalkyl group having 1 to 50 carbon atoms and perfluoroalkoxygroup having 1 to 50 carbon atoms.
 3. The LCD panel of claim 1, whereinthe hydrocarbon derivative having a perfluorocarbon group formed bypolymerizing at least one of the compounds represented by Formulas 1to4:

where a is 0 or 1, n is a natural number from 1 to 11, and A is aphotopolymerization reactive group,

where a is 0 or 1, n₃ is a natural number from 1 to 10, and A is aphotopolymerization reactive group,

where a is 0 or 1, n₄ is a natural number from 1 to 6, and A is aphotopolymerization reactive group,

where a is 0 or 1, n₅ and n₆ are natural numbers from 1 to 6,respectively, and A is a photopolymerization reactive group.
 4. The LCDpanel of claim 3, wherein the photopolymerization reactive group is(meth)acryloyl group.
 5. A LCD panel, comprising: substrates facing eachother; a liquid crystal layer disposed between the substrates; andliquid crystal alignment layers, each sandwiched between the liquidcrystal layer and a respective one of the substrates, wherein each ofthe liquid crystal alignment layers comprises a non-polyimidehydrocarbon derivative having a perfluorocarbon group, wherein thehydrocarbon derivative having the perfluorocarbon group comprises atleast one of the compounds represented by Formulas 1 to 4:

where a is 0 or 1, n is a natural number from 1 to 11, and A is aphotopolymerization reactive group,

where a is 0 or 1, n3 is a natural number from 1 to 10, and A is aphotopolymerization reactive group,

where a is 0 or 1, n4 is a natural number from 1 to 6, and A is aphotopolymerization reactive group,

where a is 0 or 1, n5 and n6 are natural numbers from 1 to 6,respectively, and A is a photopolymerization reactive group, wherein thehydrocarbon derivative having the perfluorocarbon group comprises atleast one mixture of at least one of the compounds represented byFormula 1 and at least one of the compounds represented by Formulas 2 to4.
 6. The LCD panel of claim 1, wherein the hydrocarbon derivativehaving a perfluorocarbon group comprises at least one of the compoundsrepresented by Formulas 2 to 4 and at least one compound represented byFormula 5:

where n is a natural number from 6 to 26, and A is a photopolymerizationreactive group.